EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Soiling is one of the main factors that affects the performance photovoltaics systems worldwide. This phenomenon acts absorbing, reflecting and scattering partially the incoming sunlight, reducing the intensity of radiation that reaches the solar cells. This effect depends on the characteristics of the dust particles such as size, shape, chemical composition, cumulative load of dust and surface covered by them. Due to the huge increment in solar plants located in desertic areas, it has been necessary to study the relationship of climate parameters and features of deposited dust in real conditions.

In this work, solar glass coupons were exposed to environmental (outdoor) conditions present in PV Salvador solar plant (Atacama Desert, Chile) during summer and winter campaigns. The soiling was quantified gravimetrically and characterized by X-ray diffraction and Scanning Electron Microscope. The gravimetrical data were correlated with the climatic conditions though the Pearson correlation coefficient. Besides, the degradation of optical properties of soiled coupons of glass was measured trough the spectral hemispherical transmittance.

The results of Pearson test showed a significant moderate correlation (P-value<5%) between the gravimetrical data and relative humidity for values greater than 30%. The characterization of the samples shows that the soiling of both periods is composed mainly by hygroscopic mineral as anhydrite, gypsum, calcite and halite. It was found that the deposited dust shown different physical characteristics in both campaigns and, in consequence, it produces different effects on the optical properties of glass coupons. The maximum loss of transmittance of soiled glasses was 36.2% after 49 days of exposure during the summer campaign. Finally, it was demonstrated that physical features of dust as shape, size and surface covered are more important parameters than the cumulative load of dust in terms of optical degradation of glass coupons in both campaigns.